1. Field of the Invention
The present invention relates to a drive shaft apparatus, and, in particular, to an improved drive shaft which is ideal for use as a propeller shaft for a vehicle and the like.
2. Description of the Present Art
In a drive shaft apparatus for a vehicle, such as shown, for example, in Japanese Publication of Unexamined Utility Model Application No. 59-188731, a so-called viscous clutch is interposed in the power transmission system of a four-wheeled drive vehicle with the objective of absorbing undesirable rotational variations and vibration. This viscous clutch comprises a group of resistance plates, which are positioned parallel to and close to the inside of a hermetically sealed chamber and mutually spline-mated in each shaft side member of two shafts which perform torque transmission, and a viscous fluid enclosed between those resistance plates. Then, the relative rotation is restrained by the development of a shearing resistance in the viscous fluid accompanying the relative rotation of the mutual resistance plates, and the torque is distributed. Accordingly, because there is no mutual contact of the members between the two shafts, as is seen in other coupling devices, there is no wear produced, and the differential characteristics are extremely stable and smooth.
However, because a special viscous clutch is used, that portion is heavy, and the costs are increased.